Patent GB-826547-A (GB)
Title: Improvements relating to variable-speed power transmission mechanisms for motor vehicles
IPC: F16H61/02
Filed: 1957-06-21
Abstract: 826,547. Change-speed gear. GENERAL MOTORS CORPORATION. June 21, 1957 [July 25, 1956], No. 19661/57. Class 80 (2). [Also in Groups XXIX and XXXIV] In a change-speed control for a vehicle wherein fluid pressure for engaging ratioestablishing friction brakes and a clutch is regulated in accordance with torque demand by engine manifold depression indicative of engine throttle control setting, the fall of such pressure consequent on a throttle closing movement is subject to a delay device to allow time for the drive torque to fall, such device being inoperative for throttle opening movement. Function summary.-Control of the selector brakes and clutch is only by a manual selector valve 440 having four settings: Park, P; Reverse R,; Drive, D; and Hill Retarder, HR. In D setting automatic transition between three phases is provided by three turbines T 1 , T 2 , T 3  of a driving torque converter, the first two driving through individual planet-trains and becoming over-run in succession with speed increase until the third takes over and drives direct. HR setting provides a fixed two-way drive from the first turbine only through one planet train. Extra torque multiplication is provided in the torque converter by accelerator overtravel which hydraulically pivots the blades of the reactor R from a normal low angle setting to a high angle setting, such action being prevented in reverse. Servo pressure for the clutch and brakes is regulated by manifold depression or throttle setting, pressure reduction being delayed as stated above. Clutch and brake engagement is rendered progressive by a timer valve 450. Pressure augmentation is provided in HR setting. A positive park lock 76, not described, is provided. Gear and converter arrangement.-This is similar to the arrangements described in Specifications 799,033 and 811,927, [Group XXIX], the torque converter having in addition to an impeller 12 and one-way mounted reactor R, three turbines T 1 , T 2 , T 3 , the first two being connected to the output shaft 16 respectively through sun-ring-planet trains having output-mounted planet carriers 42, 40, reaction ring and sun gears 58, 60 prevented from reverse rotation, and input sun and ring- gears 35, 37 connected to the respective turbines T 1 , T 2 . The third turbine T 3  is directly connected to output 16 through a neutral clutch 33A which is released in P, N and HR settings of the manual valve. The second train reaction sun 60 is held from reverse rotation by a releasable brake 72 acting through a one-way detent 68, and the first train reaction ring 58 is prevented from reverse rotation relative to the sun 60 by a one-way clutch 64 between the two reaction members 58, 60. The one-way clutch 64 also transmits torque when a brake 38 is applied to the second train ring 37, and the forward brake 72 is released for reverse. In forward drive, with the brake 72 applied, an input sun 35 of the first train, input ring 37 of the second, and the common output carriers 42, 40 are driven respectively by the three turbines T 1 , T 2 , T 3 , which deliver torque in succession with increase in speed as the preceding turbine is overrun. A neutral clutch 33A is arranged between the turbine T 3  and output, such clutch being released in neutral and also in Hill-Retarder setting when a brake 74 is applied to the first ring gear 58 to provide a two-way drive from the first turbine T 1  alone at the fixed reduction ratio of the first train. Torque converter details.-The blades of the reactor R are mounted on cranked hinged pins 84 engaging a piston 222 which is moved axially to the left, position shown, to set the blades at maximum incidence, " high angle," for maximum torque multiplication, by pressure in the working circuit of the converter, and is normally held in its rightward " low angle " position by opposing pressure supplied to a chamber 244, as described below, and assisted by hydrodynamic pressure on the reactor blades themselves. The second turbine T 2  has a labyrinth seal 184 in the first turbine T 1 , which latter has three spaced balance-pins 123. Vanes 429 in the input shell 104 entrain liquid to maintain centrifugal pressure between the input shell 104 and first turbine T, equal to that in the torque converter. A cap 128 seals the front of the converter housing and a seal 110 the rear. Liquid is supplied to the working circuit of the converter through an annular clearance 114 and leaves it through passages 186 in the hub of the second turbine T 2  and an annular clearance 190. Thrust bearings are provided between the various members as shown. Clutches and brakes.-The brakes 72, 38 and clutch 33A are all of the kind in which a rotating coned shell, e.g. 38, is clamped against an internal cone 194, stationary for the brakes, rotary for the clutch, by application of liqud pressure at 202 to a piston 198 having an external cone engaging the internal surface of the rotating shell 38. A wavy spring 204 releases the brake 38. The rear ring-gear brake 74, for reverse, is of the multi-disc type engaged by liquid pressure applied at 322 to a piston 320 fast to that 312 of the adjacent forward brake 72 which, together with its brake 74, is released by a wavy spring 319 which centralizes both pistons. Fluid pressure supply and regulation.-Input and output driven pumps 108, 270 supply a system main 406, Fig. 4, through check valves 402, 404, which close to that pump producing the lower pressure. A main regulator valve 408, spilling to an exhaust 418, is loaded leftwards by supply pressure 406 and rightwards by a spring 422 and pressure in a line 494 which is itself regulated in accordance with inlet manifold depression acting at 506 on a regulator valve 496, whereby system pressure varies with input torque. Delay of system pressure reduction following a sudden accelerator release is achieved by the accumulator 508 and a check valve 510. If the accelerator is suddenly depressed, the consequent reduction in engine manifold depression causes a sudden increase of pressure in the line 494. The check valve 510 is closed and pressure leaks only slowly through a restrictor 512 in the check valve to charge the accumulator 508, with little effect on the rate of pressure rise in the line 494 and main regulatorvalve chamber 492, thereby producing a rapid increase in system pressure. If, however, the accelerator is suddenly released, the consequent fall in pressure in the line 494 due to increased manifold depression is retarded by pressure in the accumulator 508 opening the check valve 510 and flowing into the line 494, thus maintaining the loading on the main regulator valve to maintain system pressure to allow time for the engine torque to reduce. In forward and reverse drive settings, D, R, the neutral clutch 33A is engaged, and pressure in its engaging chamber 156 acts through a line 486 leftwards on a differential land of the main regulator valve 408 to reduce system pressure. In Hill-Retarder setting HR, the neutral clutch 33A is exhausted, removing this leftward loading of the regulator valve and thus augmenting system pressure. Initially the input pump 108 feeds the torque converter directly through a port 416 in the main regulator valve 408 and a line 114. When the output pump 270 takes over at increased pressure the regulator valve exhausts the input pump (position shown) to save power. Fluid leaves the converter through an exit line 190, including a cooler 426 and final relief valve 424. The cooler has a by-pass valve 566 which is opened, position shown, by cooler pressure, and closed by a spring 558 and by increase of fluid temperature acting to expand wax 562 which raises a valve plunger 564. Fluid system components.-In addition to those mentioned above are a timer valve 450 which, in conjunction with an accumulator 466, renders clutch and brake engagement progressive and an accelerator operated valve 520, which controls reactor blade-angle. Operation. Manual selection.-The manual selector valve 440 controls the supply of pressure of the engaging chambers 202, 318, 156 and 322 of the reverse brake 38, forward brake 72, neutral clutch 33A and Hill-Retarder brake 74 respectively. Moving the manual valve from N or P, in which all the engaging chambers exhaust, to D (shown) causes main pressure 406 to flow to the engaging chambers 156 and 318 of the neutral clutch 33A and forward brake 72, and in doing so to pass unrestricted through a large orifice 452 in the piston 460 of the timer valve 450. Pressure initially building up in the clutch and brake forces the timer-valve piston 460 to the right, against a spring, thereby substituting a restricted orifice for the unrestricted one 452, which retards increase of brake and clutch-engaging pressure, until pressure in the clutch chamber 156 acts through a line 464 to push back the spring-loaded piston of the accumulator 466, and then pass through a line 478 to thrust back the piston of the timer valve 450 to its unrestricted left position, permitting final rapid increase in engaging pressure. Reactor blade - angle control.-The reactor blades are normally held in low-angle setting by torque-converter pressure 114, supplied through the normally open accelerator-operated valve 520 and line 232 to a chamber 244 at the left of the blade-control piston 222, to equalize the torque-converter pressure acting permanently on the right side of the piston and permit hydrodynamic pressure on the blades to move them to low angle, taking the piston 222 to the right. When the operator fully opens the engine throttle an arm 530 in the accelerator linkage moves the piston of the valve 520 to the right (position shown), to exhaust the chamber 244 through a line 534 and the manual valve 440, permitting the blade-control piston 222 to move left for high angle blade setting, giving maximum torque multiplication. Exhaust action is prevented when the manual valve 440 is in reverse setting, to